# coding=utf-8
# 过滤列表语法：
# [mapping-expression for element in source-list if filter-expression]

def filter_lst(lsts=None):

    if lsts:
        return [lst for lst in lsts if len(lst) > 3]
    return None
    
if __name__ == '__main__':
    print filter_lst(['a', 'bb', 'ccc', 'dddd', 'eeeee'])